An analysis of the 1851 census indicates that the population was 52.3 per cent female and 47.7 per cent male. These figures are derived from a: 99.4 per cent sample, taking 1,970 of the inhabitants, as compared with the total population of 1,982: there being 569 males (28.9 per cent), 371 boys under the age of fourteen (18.8 per cent); 710 females (36 per cent) and 320 girls under the age of fourteen (16.2 per cent). (This 99.4 per cent sample will be used throughout the following analysis.)

The fact that the town had more females than males is not particularly significant, as this has proved to be the result of every census taken here. It is of interest, however, that just over one-third of the population were under fourteen years of age, and shows that Peebles had a very young population. This is possibly due to the great number of people who had come into the town, for they were mostly younger men and women looking for work.

The large number of migrants living in the town in 1851 is very impressive because they were settled in Peebles before the coming of the railways. They had made the journey when travel was difficult and more suited to younger rather than older travellers, especially when coming from a long distance. An analysis of the birth-place of each head of household shows the extent of such inwards migration and is a guide to where the newcomers had originated. There were 443 households in the 99.4 per cent sample and this indicated that 39.8 per cent (176 heads) were born in Peebles and 17.8 per cent (seventy-nine heads) were born in others parts of Peeblesshire. Therefore, some 57.6 per cent of the heads of household were born within the 'shire'. However, from farther afield 20 per cent (eighty-nine heads) came from the counties bordering Peeblesshire and about 15.1 per cent (sixty-seven) were born in other parts of Scotland. The remaining 7.2 per cent (thirty-two heads) were born outside of Scotland: nineteen in Ireland, eleven in England, and two in France.

Most of the heads of household who were incomers appeared to be settled in the town and had children who were born in Peebles. The sample showed there were 55.6 per cent (1,096) born in Peebles, 13 per cent (256) born in Peeblesshire, 24.6 per cent (484) born in other parts of Scotland, 2.2 per cent (forty-four) born in England, 3.6 per cent (seventy) born in Ireland and 1.0 per cent (eighteen) born overseas; the places of birth of two are not shown.

There were boarding schools in Peebles and the census showed that there were eight boarders born in East India, three in Van Diemens Land (Tasmania) and two in Jamaica.